Which is the best space propulsion method?

Wikipedia has an excellent article on space propulsion. Let us assume that less expensive cargo costs will create a demand for space transportation due to raw materials/energy/unique conditions in space. Similar to when earlier railroads created their own demand when they lowered transportation costs. Do you have any idea which of the proposed propulsion will be best in the near and far future?

Staff: Mentor

It depends on the purpose, but ion propulsion is the most promising in terms of efficiency (impulse vs mass). The problem is that its a low thrust for a long duration so not good for launch, just for long-duration missions.